The major goal of this research is the refinement of a theory of mental activity. This theory is based on the premise that all psychological phenomena can be explained in terms of mental activity, without reference to the metaphysical constructs of mental mechanism. The theory is described and its predictions are systematically applied to the existing data. These data are not adequate to test the predictions having to do with automatization of mental activity, so the proposed experiments are designed to determine the character and components of this phenomenon. Twelve measures of automatization are derived from the theory and used in the design of the proposed experiments. There are four series of experiments, having to do with divided attention, the speed of perception, mental preparation, and context effects.